Hydraulic fracturing with foam fluids or "foam fracturing" is described in U.S. Pat. No. 3,937,283. This process involves the generation of a foam of a desired quality. Various gases and liquids may be used to create the foam, but the usual foams are made from nitrogen or carbon dioxide and water in the presence of a suitable foaming agent. The foam is pumped into the formation at a temperature and pressure sufficient to cause a fracture in the subterranean formation.
Fracturing caused by a foam fracturing process is effective and has advantages over the known prior art methods. For example, foam fracturing can be carried out without significant fluid loss in comparison to treatments utilizing unfoamed liquids. Additionally, foam comes out of the well easily when pressure is removed from the wellhead, because of the expansion of the foam when the pressure is released.
In fracturing operations, as disclosed by Conway et al. in U.S. Pat. No. 4,453,596, a gelled foam fluid is injected into a wellbore under sufficient pressure to create at least one fracture in a subterranean formation. An additional quantity is pumped into the formation after creation of the fracture to extend the length of the fracture. Thereafter, pressure applied to the fluid is reduced whereby said foam is caused to collapse and deposit into the fracture a particulate present in the fluid thereby propping the fracture.
Long horizontal wells are increasingly becoming common in steam operations in heavy oil reservoirs. Non-uniform distribution of heat due to reservoir heterogeneities and pressure drop within the well, commonly results in poor oil production.
Therefore, what is needed is a foam/steam injection method for fracturing a formation containing a horizontal wellbore so as to obtain sequential fractures along its length and uniform heating along said wellbore.